THE astonishing improvement in diesel performance, economy and refinement over the last 15 years has come largely from advances in electronically controlled high-pressure common-rail fuel injection and turbocharger technology.
High fuel pressure means fuel is injected into the combustion chamber in distinct ‘squirts’ for each combustion event, allowing combustion to be optimised for performance or economy – or anywhere in between – depending on the demand. The commonrail’s partner is the fast-switching piezo-crystal injector that has largely replaced the slower electromagnetic solenoid injector.
Turbochargers benefit most from variable vane geometry, which helps the trade-off between turbo response and pumping capacity. Sequential turbos, where small and large turbos work together, do an ever better job of addressing these two conflicting demands.
Plus, diesel compression ratios have dropped from about 22:1 to around 16:1 for refinement, quieter operation, less knock, and lower NOX emissions.